DE3133708

The extruder for processing polymer materials contains a heated cylindrical barrel with a filling hopper, in the hollow space of which cylindrical barrel there are accommodated, coaxially, a rotating helical screw with, arranged one after the other in the flow direction of the material, a feed zone, compression zone and metering zone and a bush which surrounds the screw in the feed zone and has parallel helical grooves formed on its inner surface, in which grooves the direction of the turn of the helical lines is opposite to the direction of the helical line of the screw, the pitch of the helical line of the screw differing from the pitch of the helical line of the grooves. According to the invention, the pitch of the helical line of the bush grooves is less than the pitch of the helical line of the screw and is calculated according to the following relationship: in which t2 represents the pitch of the helical line of the helical grooves on the inner surface of the bush; t1 represents the pitch of the helical line of @ the screw; phi represents the pitch angle of the helical line of the screw; K represents the ratio of the specific weight of the melt to the bulk density of the starting material; epsilon represents the degree of pressure loading of the screw.